BEIRUT - Some Islamist groups fighting in Syria have rejected the announcement of an Islamic caliphate by an increasingly powerful rival.

Nine groups, including fighters and religious scholars, have dismissed the statement by Islamic State, an al-Qaida offshoot which declared its leader ruler of the Muslim world on Sunday after military gains in neighboring Iraq.

The group, formerly called the Islamic State in Iraq and Syria or ISIS, has seized parts of eastern Syria and western Iraq but is still battling rival Islamist fighters in Syria.